It is known to use a hot filament ion source in a system for detecting and counting ions. Atoms, originating from a source of atoms, present near the hot filament are ionized and the ions formed are reemitted. The reemitted ions form a beam that is focused in the direction of ion detecting and counting modules using ion extracting electrodes and a magnetic field.
The document “Optimisation of a Langmuir-Taylor detector for lithium” by R. Delhuille et al. (Rev. Sci. Instrum. 73, 2249 (2002)) describes a system for detecting and counting ions comprising a source of atoms, a hot filament ion source, ion extracting electrodes and ion detecting and counting modules. The filament of the ion source takes the form of a substantially flat strip, in other words the filament is a straight flat strip.
The operating principle of this system for detecting and counting ions may be summarized as follows: a source of atoms emits a gas composed of atoms. The atoms of the gas strike the hot filament, said filament has a work function higher than the ionization energy of the atoms. One or more judiciously placed extracting electrodes, possibly encircling the filament, facilitate the reemission of the ions, the trajectory of the latter being oriented toward the source of atoms. A magnetic field then deviates the trajectory of the ions toward the detecting and counting modules.
One drawback of the aforementioned system, such as described in the document, resides in the fact that only a certain percentage, typically 50%, of the ions emitted by the hot filament is focused on the ion detecting and counting modules, thereby leading to a substantial loss of said ions at the detecting modules.